RollOverTheFloor's New York City Subway track layout changes
IRT White Plains Road Line north of East 180th Street and south of Jackson Avenue 142nd Street Junction North of 135th Street station on the IRT Lenox Avenue Line is where trains can either continue on Lenox Avenue to 145th Street and 148th Street – Lenox Terminal stations or diverge northeast to the IRT White Plains Road Line in the Bronx. Also, 135th Street station is two-tracks instead of three-tracks and there isn't a diamond crossover between the two tracks until just to the east of 148th Street – Lenox Terminal station; lastly, 145th Street is a full-length 510 feet IRT station instead of half-length. Nostrand Junction Just at the east end of the Franklin Avenue station is where trains can either continue on Eastern Parkway or diverge south to the IRT Nostrand Avenue Line. Further east, the northbound local track descends to a lower level directly below the southbound local track; then, the northbound express track, which is still on the upper level at this point, descends to the lower level directly below the southbound express track, creating a dual level two-over-two track layout. A switch on the upper level allows southbound express trains to change to the local track and a corresponding switch on the lower level allows trains on the northbound local track to change to the express one. This, however, can be a bottleneck for southbound '''2''' and '''5''' trains as they merge into one pair of track further east of the station. However, at least this doesn't affect southbound local '''3''' and express '''4''' trains, which continue on Eastern Parkway. Because, when a southbound '''2''' and '''5''' arrive at Franklin Avenue at the same time, they leave together at the same time also, but one of them gets held in their own tunnel to let the other proceed further south into the President Street on the IRT Nostrand Avenue Line. Likewise, heading west into Franklin Avenue, northbound '''3''' and '''4''' may arrive and then leave there at the same time; this delays a northbound '''2''' or '''5''' train. However, if the '''5''' comes first but is delayed by a '''4''' ahead, it sits in the tunnel for 2 minutes. Afterwards, the '''2''' will be immediately right behind the '''5''', allowing both northbound local and express to platform together for a connection. This ultimately means minor delays, yet with opportunities. Homeball Alley Just at the south end of 145th Street station, the track work is quite complex. On the upper level, the express tracks end at bumper blocks. However, two tracks then form beginning between the local tracks, also on the upper level, and the lower level express tracks, which begin to rise to the upper level at this point, in each direction. On the lower level, before the local and express tracks begin to rise to the upper level, there are diamond crossovers and switches between all of them. Afterwards, the local tracks rising from the lower level merges with those on the upper level; while the express tracks rising from the lower level feed the rest of the IND Eighth Avenue Line express tracks, with diamond crossovers between those tracks and the aforementioned middle tracks in each direction, just before the line is shorten to six tracks and enters 135th Street station. The express trains use the innermost pair of tracks and the locals use the outermost tracks. The middle tracks, at this point, are lay-up tracks and not normally used by trains in passenger service. These tracks then end just north of 125th Street station, where they merge with either the express or local tracks; then there are diamond crossovers and switches between all remaining tracks just before the line enters 125th Street station. This entire section of the IND Eighth Avenue Line, between 145th Street and 125th Street stations, is nicknamed "Homeball Alley" due to the large amount of switches, signals, splits, diverges, and merges in the area. South of 59th Street – Columbus Circle station on the IND Eighth Avenue Line South of 59th Street – Columbus Circle station on the IND Eighth Avenue Line is where trains can either continue on Eighth Avenue or diverge to the Seventh Avenue – 53rd Street station via the IND Sixth Avenue Line express tracks. This track layout allows southbound '''A''' and '''C''' trains, without any sort of delays, to continue through the station rather than one or the other being held by either the '''B''' or '''D''' ahead. However, '''B''' and '''D''' trains that enter, stop, and leave the station at the same time get held in the tunnel south of the station, while one of them proceeds to Seventh Avenue – 53rd Street station first before the other does. This track layout allows northbound '''B''' and '''D''' trains to continue pass Seventh Avenue – 53rd Street station without any sort of delays. However, one or the other or both of them get held in their own tunnel respectively if an '''A''' or '''C''' or both the '''A''' and '''C''' are already entering 59th Street – Columbus Circle station (depending on the trains being ahead of schedule or behind schedule). This sort of delay eventually allows both the '''B''' and '''D''' to platform at the station for a connection. IND Grand Concourse Line The IND Grand Concourse Line runs north to south through the Bronx and portions of Harlem, parallel to the mostly-elevated IRT Jerome Avenue Line which lies between the two and four blocks to the west for its entire length in the Bronx. It begins as a two-track subway at Norwood – 205th Street, running east-to-west underneath East 205th Street, then private property, then for a short portion under Van Cortland Avenue. West of Norwood – 205th Street is a diamond crossover which allows trains that originate/terminate at the station to reach the correct track. A center track then forms, which leads to the Grand Concourse yard. The line then curves south at Mosholu Parkway to Grand Concourse, from which it derives its name, at 206th Street. Two tracks from the Grand Concourse yard arrive between the two revenue tracks with switches and diamond crossovers between all four of them before entering Bedford Park Boulevard. This is where the local/express split begins, with the local tracks coming from the yard and the express tracks coming from Norwood. Contrary to standard practice, the local tracks are in the center and the express tracks are on the outside. South of this station are diamond crossovers between the two center tracks, allowing originating/terminating local trains to reach the correct track and without the need to use the switches north of the station to relay local trains. After this, each of the four tracks cross over one another to form the regular local-outer/express-inner configuration before entering Kingsbridge Road. The line then runs south, with switches and diamond crossovers between all four tracks just north of Tremont Avenue. Due to the terrain, the vicinity of 174th–175th Street station is uniquely built both underground and over 175th Street. The line curves west before 161st Street – Yankee Stadium station, with switches and diamond crossovers between all four tracks west of that station, and passes under the Harlem River into Manhattan via the Grand Concourse Tunnel. There is one more stop, 155th Street, then the line curves south, with a diamond crossover between the express tracks, just before it joins the IND Eighth Avenue Line at the lower level of 145th Street station. Permanent G Train Extension to 18th Ave DeKalb Avenue Junction Coney Island Terminal BMT Nassau Street Line Other changes